The present invention relates to a process for processing an exposed color reversal photographic film, enabling reduced water consumption and preventing the formation of biofilms resulting from the proliferation of microorganisms in the final washing baths of the processing.
For ecological and economic reasons, the reduction of water consumption of processes for processing photographic films is subject to many efforts on the part of the photographic industry. In particular, for processing an exposed color reversal photographic film, it is common to use a final washing zone, comprising several washing baths placed in series. The water for each washing bath is supplied by a counter flow, coming from the bath located downstream, and the replenishment is done in the washing bath furthest from the fixing bath or in the final rinsing bath. However, the retention time for water in this washing zone is increasing, which encourages in these baths the growth of microorganisms (bacteria, yeasts and molds) that develop thanks to the presence of chemical compounds. The presence of these chemical compounds is caused by the carry-over of significant quantities of solutions coming from the processing baths during the passage of the photographic film from tank to tank, either by the photographic film itself, or by the belts used for conveying the photographic film. The proliferation of these microorganisms causes the formation of biofilms increasing the turbidity of the water. This is harmful to the quality of the developed films and maintenance stoppages are required to clean the installations. This problem is more particularly encountered when the washing baths are seasoned, i.e. contaminated by the presence of chemical compounds coming from the baths located upstream in the processing and when the installations are used intermittently as in small photographic processing units or minilabs.
The present invention provides a method for processing an exposed color reversal photographic film enabling the problems mentioned above to be solved.
The method of the present invention for processing an exposed color reversal photographic film comprises the steps of successively: (1) first black and white developing, the exposed film; (2) subjecting the film developed in (1) to a reversal procedure; (3) color developing; (4) bleaching; (5) fixing and (6) circulating the film after the fixing bath in a final washing zone comprising at least one washing bath, wherein
at least one washing bath of said final washing zone comprises a buffer, comprised of a weak acid and its conjugated base, with a conjugated base concentration more than or equal to 1 g/l, said buffer being capable to maintain the pH between 4.5 and 6 in said washing bath, and
after having collected the contents of said washing bath, the said contents are passed through a nanofiltration device, comprising a membrane whose cut-off threshold is more than the molar mass of the weak acid and the conjugated base of the buffer, to give a permeate that is recycled in said final washing zone.